1. Field of the Invention
The present invention relates to an encoding circuit for achieving a high compression ratio in encoding video signals.
2. Description of the Related Art
The MPEG technique, one of the commonly employed conventional encoding techniques, is based on the principal of orthogonal transformation through inter-frame prediction coding and DCT (discrete cosine transform) and utilizes motion vectors to strengthen correlation between frames, thereby improving prediction accuracy and further enhancing the compression ratio. Another compression method for a DVC (digital video cassette) is based on DCT and an encoding method in which groups of encoding blocks are provided and such groups are combined to average the overall amount of generated codes (DV format). Other techniques include DPCM (differential pulse code modulation) and prediction coding. Further, Hadamard transform is also known as another encoding method.
However, as can be imagined from the basic principle thereof, both the MPEG and DV formats require a large encoding circuit, while other techniques which do not require large scale encoding circuits, such as DPCM and prediction coding, cannot be expected to achieve a high compression ratio.